$editor_settings = array('dfw' => true,'quicktags' => false);
wp_editor( $postcontent, 'postcontent', $editor_settings );

function mce_inline( $init ) {

    $init['inline'] = true;

    return $init;
}
add_filter('tiny_mce_before_init', 'mce_inline');

<div class="editable" style="width:100%; height:550px">
This is an editable div element element.
</div>